KVM: set_memory_region: Refactor prepare_memory_region()

This patch drops the parameter old, a copy of the old memory slot, and
adds a new parameter named change to know the change being requested.

This not only cleans up the code but also removes extra copying of the
memory slot structure.
Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/arm/kvm/arm.c

@@ -230,8 +230,8 @@ int kvm_arch_set_memory_region(struct kvm *kvm,
 
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *memslot,
-				   struct kvm_memory_slot old,
-				   struct kvm_userspace_memory_region *mem)
+				   struct kvm_userspace_memory_region *mem,
+				   enum kvm_mr_change change)
 {
 	return 0;
 }

arch/ia64/kvm/kvm-ia64.c

@@ -1560,8 +1560,8 @@ int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages)
 
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 		struct kvm_memory_slot *memslot,
-		struct kvm_memory_slot old,
-		struct kvm_userspace_memory_region *mem)
+		struct kvm_userspace_memory_region *mem,
+		enum kvm_mr_change change)
 {
 	unsigned long i;
 	unsigned long pfn;

arch/powerpc/kvm/powerpc.c

@@ -412,8 +412,8 @@ int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages)
 
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *memslot,
-				   struct kvm_memory_slot old,
-				   struct kvm_userspace_memory_region *mem)
+				   struct kvm_userspace_memory_region *mem,
+				   enum kvm_mr_change change)
 {
 	return kvmppc_core_prepare_memory_region(kvm, memslot, mem);
 }

arch/s390/kvm/kvm-s390.c

@@ -974,8 +974,8 @@ int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages)
 /* Section: memory related */
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				   struct kvm_memory_slot *memslot,
-				   struct kvm_memory_slot old,
-				   struct kvm_userspace_memory_region *mem)
+				   struct kvm_userspace_memory_region *mem,
+				   enum kvm_mr_change change)
 {
 	/* A few sanity checks. We can have exactly one memory slot which has
 	   to start at guest virtual zero and which has to be located at a

arch/x86/kvm/x86.c

@@ -6906,23 +6906,21 @@ int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages)
 
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				struct kvm_memory_slot *memslot,
-				struct kvm_memory_slot old,
-				struct kvm_userspace_memory_region *mem)
+				struct kvm_userspace_memory_region *mem,
+				enum kvm_mr_change change)
 {
-	int npages = memslot->npages;
-
 	/*
 	 * Only private memory slots need to be mapped here since
 	 * KVM_SET_MEMORY_REGION ioctl is no longer supported.
 	 */
-	if ((memslot->id >= KVM_USER_MEM_SLOTS) && npages && !old.npages) {
+	if ((memslot->id >= KVM_USER_MEM_SLOTS) && (change == KVM_MR_CREATE)) {
 		unsigned long userspace_addr;
 
 		/*
 		 * MAP_SHARED to prevent internal slot pages from being moved
 		 * by fork()/COW.
 		 */
-		userspace_addr = vm_mmap(NULL, 0, npages * PAGE_SIZE,
+		userspace_addr = vm_mmap(NULL, 0, memslot->npages * PAGE_SIZE,
 					 PROT_READ | PROT_WRITE,
 					 MAP_SHARED | MAP_ANONYMOUS, 0);
 

include/linux/kvm_host.h

@@ -479,8 +479,8 @@ void kvm_arch_free_memslot(struct kvm_memory_slot *free,
 int kvm_arch_create_memslot(struct kvm_memory_slot *slot, unsigned long npages);
 int kvm_arch_prepare_memory_region(struct kvm *kvm,
 				struct kvm_memory_slot *memslot,
-				struct kvm_memory_slot old,
-				struct kvm_userspace_memory_region *mem);
+				struct kvm_userspace_memory_region *mem,
+				enum kvm_mr_change change);
 void kvm_arch_commit_memory_region(struct kvm *kvm,
 				struct kvm_userspace_memory_region *mem,
 				struct kvm_memory_slot old);

virt/kvm/kvm_main.c

@@ -856,7 +856,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
 		slots = old_memslots;
 	}
 
-	r = kvm_arch_prepare_memory_region(kvm, &new, old, mem);
+	r = kvm_arch_prepare_memory_region(kvm, &new, mem, change);
 	if (r)
 		goto out_slots;